Weldability of GH3539 superalloy: Unraveling the dueling roles of Zr, C, and Si in solidification crack formation and healing

Weld solidification cracking critically impedes the application of the advanced GH3539 alloy, with susceptibility profoundly linked to trace element composition. This study systematically deconstructs the competing metallurgical mechanisms by investigating the distinct roles of Zr, C, and Si. Our findings reveal a complex duality: Zr acts as a singular embrittling agent, significantly widening the solidification temperature range and forming low-cohesion liquid films that promote extensive unhealed crack propagation. In contrast, C and Si play a dualistic role. Although their segregation promotes the formation of crack-susceptible eutectic liquid films (embrittlement), it simultaneously introduces a competing mechanism for healing cracks. The voluminous M 6 C eutectic liquid formed at high C and Si concentrations effectively backfills nascent microcracks. Despite this partial healing, the net effect still increases crack susceptibility, indicating that embrittlement kinetics dominate over backfilling under the applied strain. This study provides a mechanistic understanding of the competition between crack formation and repair, offering crucial insights for the compositional design of crack-resistant welding consumables for the GH3539 alloy.